How do people do their own RDNS without a full class C ?

[Kyle R. Green]

On Tuesday, January 8, 2002, at 10:36 PM, Patrick Thomas wrote:

> Yes, but the problem is, I am running many many domains out of my 64
> addresses, so it is not possible for them to simply add in generic PTRs
> for each IP all pointing to the same .yourdomain.com ...

Well, doesn't really matter:

[Please note the ending dots that I forgot in the previous examples.]

0.168.192.in-addr.arpa:

5     IN     CNAME     192-168-0-5.yourdomain.com.
6     IN     CNAME     192-168-0-6.yourdomain.com.
7     IN     CNAME     192-168-0-7.yourdomain.com.

yourdomain.com:

192-168-0-5     IN     PTR     www.yourdomain.com.
192-168-0-6     IN     PTR     www.someotherdomain.com.
192-168-0-7     IN     PTR     www.yetanotherdomain.com.

The remote clients/servers will query the server authoritative for 
0.168.192.in-addr.arpa to find out what the PTR for 5.168.192.in-
addr.arpa is.  The CNAME will be encountered, resulting in another 
request to yourdomain.com's nameservers to find out what the PTR for 
192-168-0-5.yourdomain.com is.  www.yourdomain.com. will be returned.  
It's a cheap hack that works, although I can't guarantee that it's 100% 
RFC compliant.

It probably would never get the ISC Seal of Approval(TM).

--
Kyle R. Green
kyle at kgreen.org

Delores breezed along the surface of her life like a flat stone forever 
skipping along smooth water, rippling reality sporadically but oblivious 
to it consistently, until she finally lost momentum, sank, and due to an 
overdose of flouride as a child which caused her to suffer from chronic 
apathy, doomed herself to lie forever on the floor of her life as 
useless as an appendix and as lonely as a five-hundred pound barbell in 
a steroid-free fitness center.
         -- Winning sentence, 1990 Bulwer-Lytton bad fiction contest.